1. Field of the Invention
The present invention relates to multi-color concrete tiles, particularly concrete roof tiles, and to methods and apparatus for making same.
2. History of the Prior Art
Various methods have been employed for making concrete tiles, such as concrete roof tiles. The particular methods used depend on such things as the shape of the tiles being formed. Typically, wet concrete is dispensed onto a moving pallet, following which the pallet is passed under a roller and slipper to form and then shape the tile. A knife assembly chops and shapes the opposite edges of the tile. The wet concrete is cured and then removed from the pallet to provide the completed tile.
In a known method of making concrete roof tiles, a conveyor is used to transport the wet concrete from either a continuous mixer or a batch mixer to a making head assembly disposed above a conveyor containing a succession of moving pallets, arranged end-to-end. The pallets define the general shape of the tiles to be formed. As each pallet passes within the making head assembly, wet concrete is dispensed onto the pallet, with the help of a rotating roller which meters the concrete onto the pallet and compresses the wet concrete to a desired thickness. The pallet is then passed beneath a slipper which engages the wet concrete and has a profile selected to provide the concrete with a desired cross-sectional configuration. A knife assembly chops the continuous ribbon of concrete formed on the end-to-end succession of pallets to define the individual tiles and to shape the edges thereof. The pallets with the wet concrete extruded, compressed, shaped and chopped thereon are then separated and advanced to a racker, where the pallets are loaded onto racks for transport to a curing facility. The curing facility typically comprises an oven in which the tiles are heated at a desired temperature and for a desired period of time to cure the concrete. Following that, each concrete tile is removed from its supporting pallet to thereby provide the completed concrete tiles.
Concrete tiles formed in the manner described may be provided with a desired color or combination of colors. Typically, a coloring pigment is added to the wet concrete during the mixing process therefor, so that the concrete tiles will have a desired color. The tiles may also be colored by spraying a coloring slurry onto the tiles following extrusion of the tiles onto the pallets and while the concrete is still wet. A method for randomly coloring the tiles with different coloring slurries is described in U.S. Pat. No. 4,743,471 of Shills, which issued May 10, 1988 and which is commonly assigned with the present application.
In the method of random coloring described in U.S. Pat. No. 4,743,471, concrete roof tiles which are formed by conventional extrusion equipment on moving pallets are sequentially advanced from the making head assembly and the knife assembly by a conveyor to a base applicator which sprays a base coat of coloring slurry over essentially the entire top surface of each tile. One or more overspray applicators located downstream from the base applicator then spray additional colors over different portions of the top surfaces of the tiles in intermittent, randomly varying fashion so that the color pattern on each tile is essentially unique and is not repeated on any other tile. The overspray applicator includes a blade which is gated into contact with a rotating drum to apply coloring slurry to a rotating cylindrical brush in intermittent, randomly varying fashion and which is moved across the brush to vary the spray pattern across the width of the passing tiles in intermittent, randomly varying fashion.
While the coloring method described in U.S. Pat. No. 4,743,471 is useful in applying two or more colors to a tile in a pleasing artistic fashion, such technique cannot be used in the formation of all multi-color tiles. An example where such technique cannot be used is one in which two or more colors on a tile are to be distinctly separated along color dividing lines. In such instances, the technique described in U.S. Pat. No. 4,743,471 may not be capable of keeping two different and adjacent colors on a tile distinctly separated, inasmuch as such technique typically causes the two colors to spill over on each other in wavy, non-uniform, non-straight line fashion.
It would therefore be desirable to provide a method of making concrete tiles in which two different colors within a tile can be separated along a distinct color dividing line. This is particularly useful, for example, when forming tiles having one or more longitudinal grooves which separate the different colored portions thereof in a manner which creates the impression of a plurality of distinct and separate tiles of different color.